Câu 3e 

\(\left(2x+1\right)^2=\left(x-1\right)^2\)

\(\left[{}\begin{matrix}2x+1=x-1\\2x+1=1-x\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=0\end{matrix}\right.\)

1. are doing

2. were waiting

1. are doing             2. were waiting                 3. playing              4. visited         5. have not met

6. to see                7. left                  8. eating           9. passing                 10. to save

C

C

C

D

A

mờ quá

chụp cũng ko xong

\(A=\left(1+3+3^2\right)+...+3^{99}\left(1+3+3^2\right)\)

\(=13\cdot\left(1+...+3^{99}\right)⋮13\)

C

D

A

C

B

A